Membrane-type safety device



Oct. 18, 1966 A. VAN DOP MEMBRANE-TYPE SAFETY DEVICE Filed Nov. 1'7, 1964 INVENTOR:

ADRIANUS VAN DOP BYtj/mma f HIS ATTORNEY United States Patent 3,279,647 MEMBRANE-TYPE SAFETY DEVICE Adrianns van Dop, Vlaardingen, Netherlands, assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware Filed Nov. 17, 1964, Ser. No. 411,929 Claims priority, application Netherlands, Nov. 20, 1963, 300,717 2 Claims. (Cl. 220-89) The invention relates to a safety device of the frangible diaphragm type, which prevents the pressure in a vessel from rising above or falling below a certain value.

In many applications where fluids are stored in tanks and vessels it is desirable to maintain the pressure at a set value. When the pressure varies from the set value it is necessary to vent the tank to the atmosphere to prevent dangerous conditions from developing. In the past frangible diaphragms have been used to protect these tanks. Means are provided for breaking the frangible diaphragm when the pressure varies from the set value. While the use of frangible diaphragms is a satisfactory solution past equipment required the use of two diaphragms if the storage tank was to be protected against both under and over pressures.

This invention solves the problem of breaking the frangible diaphragm by providing a mechanism that responses to either under or over pressure within the tank. The pressure responsive mechanism releases a rotatable bar that free falls to break the frangible diaphragm. The mechanism includes a chamber that is divided by a diaphragm with the diaphragm being subject to the vessel pressure on one side and atmospheric pressure on the opposite side. The movement of the diaphrgam is used to release a latch that holds the rotatable bar in a vertical position. When the bar is released it falls by gravity and breaks the frangible diaphragm.

The invention will be more easily understood from the following description of a preferred embodiment when taken in conjunction with attached drawing.

The drawing is a vertical section of the safety device.

Reference numeral 1 designates the upper wall of a vessel, for example, a storage tank for petroleum products that is to protected against excessive changes in pressures. The interior 2 of the vessel is provided with a passageway 3 which communicates with the atmosphere, and is sealed by a frangible diaphragm 4 made of a suitable material such as, for example, plastic film, metal or glass. In the case of a storage tank for petroleum products the passageway 3 may, for example, be the manhole of the tank. The frangible diaphragm 4 is clamped between a flange 5 and a ring 6 with the ring being secured against the flange 5 by means of bolts (not shown). An outwardly projecting support plate 7 bearing an upwardly projecting post 8 is secured to the flange 5 by any desired means such as welding or the like. A pin or spindle 9 fitted to the element 8 provides a support for the rotable bar 10. The bar 10 is adapted to rotate around the pin or spindle 9 with the bar 10 being provided with a cutting edge 11. In addition it may be desirable to Weight the bar 10 to insure that it will generate suflicient force to fracture the diaphragm 4. The element 8 and the bar 10 are preferably made of corrosion-resistant material, for example, stainless steel or a molded plastic. The support plate 7 is provided with an actuating means 12. The actuating means 12 is a diaphragm type and consists of a closed chamber 13, which is divided into two chambers, 14 and 15, by a diaphragm 16. Chamber 14 communicates with the atmosphere by means of a vent 30 and chamber 15 communicates with the interior of the vessel 2 through a line 17. A plate 18 and a rod 19 are secured to the center of the diaphragm 16 by means of a bolt or the like. The free end 20 of the rod 19 is close to or contacts the right side of the rotable bar 10. A lever 21 is rotatably secured to the rod 19 by means of a pin 22. The lever 21 has an L shape with its free end 26 being close to or contacting the rotatable bar 10. A pin 23 is rigidly secured to the wall of the chamber 13 and lies in the plane of the lever 21. A second pin 24 is likewise rigidly secured to the wall of the chamber 13 and is provided with a ball shaped end 31. A spring latch 25 secured to the rotatable bar 10 co-operates with the ball shaped end of the pin 24 to retain the rotatable bar in a vertical position.

The safety device described operates as follows:

It is assumed that the pressure in the vessel 2 tends to exceed the maximum permissible value. The pressure is transferred to the chamber 15 through the line 17. The pressure acts on the diaphragm 16 and causes an elastic deformation thereof so that the rod 19 moves axially to the left and the free end 20 dislodges the rotatable bar 10 out of its vertical position. As a result, the bar 10 rotates to the left and ruptures or fractures the frangible diaphragm 4 with its cutting edge 11, thereby establishing communication between the interior 2 of the vessel and the atmosphere.

If the pressure in the vessel tends to fall below the minimum permissible value, the rod 19 will move to the right. As a result, the free end 26 of the L-shaped lever 21 is moved to the left and dislodges the rotatable bar 10 out of its vertical position. As a result, the bar 10 rotates to the left and ruptures the frangible diaphragm 4 with its cutting edge 11, thereby establishing communication between the interior 2 of the vessel and the atmosphere.

When the bar 10 has ruptured the frangible diaphrgam 4, the bar is in a substantially horizontal position so that from a distance it can be seen that the device has operated and that the frangible diaphragm 4 should be replaced. When the damaged diaphragm 4 has been replaced by a new one, the bar 10 is restored to its original substantially vertical position or position of rest. The clamp 25, which cooperates with the pin 24, holds the bar 10 in the vertical position.

I claim as my invention:

1. A safety device of the frangible diaphragm type that prevents the pressure in a vessel from rising above or falling below a predetermined value, said device comprising:

a frangible diaphragm, said diaphragm being disposed to seal a passageway between the interior of said vessel and the atmosphere;

a rotating bar, said bar being rotatably mounted adjacent said diaphragm and normally retained in a vertical position, said bar in addition falling to a horizontal position to rupture said diaphragm When dislodged from said vertical position;

an actuating means including a closed chamber having a diaphragm disposed therein to divide said closed chamber into first and second chambers, said first chamber communicating with said vessel and said second chamber communicating with the atmosphere;

a first rod, said first rod being fastened to the diaphragm rotating bar;

an L-shaped lever, one end of said lever being rotatably connected to said rod, the other end of said lever being disposed adjacent said rotating bar; and

a second rod, said second rod being fixedly mounted and projecting towards said rotating bar, the end of said second rod terminating adjacent said L-shaped lever to force said lever into engagement with said rotating bar when said first rod is moved away from said rotating bar.

2. The safety device of claim 1 wherein a spring loaded clamp is disposed to engage said rotating bar and retain it in a vertical position.

References Cited by the Examiner UNITED STATES PATENTS 1 2,304,417 12/1942 Mason 22089 2,514,147 7/1950 Thomas 22089 2,788,794 4/ 1957 Holinger 22089 10 THERON E. CONDON, Primary Examiner.

RAPHAEL H. SCHWARTZ, Examiner. 

1. A SAFETY DEVICE OF THE FRANGIBLE DIAPHRAGM TYPE THAT PREVENTS THE PRESSURE IN A VESSEL FROM RISING ABOVE OR FALLING BELOW A PREDETERMINED VALUE, SAID DEVICE COMPRISING: A FRANGIBLE DIAPHRAGM, SAID DIAPHRAGM BEING DISPOSED TO SEAL A PASSAGEWAY BETWEEN THE INTERIOR OF SAID VESSEL AND THE ATMOSPHERE; A ROTATING BAR, SAID BAR BEING R%OTATABLY MOUNTED ADJACENT SAID DIAPHRAGM AND NORMALLY RETAINED IN A VERTICAL POSITION, SAID BAR IN ADDITION FALLING TO A HORIZONTAL POSITION TO RUPTURE SAID DIAPHRAGM WHEN DISLODGED FROM SAND VERTICAL POSITION; AN ACTUATING MEANS INCLUDING A CLOSED CHAMBER HAVING A DIAPHRAGM DISPOSED THEREIN TO DIVIDE SAID CLOSED CHAMBER INTO FIRST AND SECOND CHAMBERS, SAID FIRST CHAMBER COMMUNICATING WITH SAID VESSEL AND SAID SECOND CHAMBER COMMUNICATING WITH THE ATMOSPHERE; A FIRST ROD SAID FIRST ROD BEING FASTENED TO THE DIAPHRAGM OF SAID ACTUATING MEANS AND PROJECTING TOWARDS SAID ROTATING BAR; AN L-SHAPED LEVER, ONE END OF SAID LEVER BEING ROTATABLY CONNECTED TO SAID ROD, THE OTHER END OF SAID LEVER BEING DISPOSED ADJACENT SAID ROTATING BAR; AND A SECOND ROD, SAID SECOND ROD BEIGN FIXEDLY MOUNTED AND PROJECTING TOWARDS SAID ROTATING BAR, THE END OF SAID SECOND ROD TERMINATING ADJACENT SAID L-SHAPED LEVER TO FORCE SAID LEVER INTO ENGAGEMENT WITH SAID ROTATING BAR WHEN SAID FIRST ROD IS MOVED AWAY FROM SAID ROTATING BAR. 